Use system QScintilla

[adridg]

Summary

The find module for QScintilla included with sqlitebrowser has never worked
(well) on FreeBSD. This port used the embedded copy of QScintilla. Fix that
up, and switch to using the system QScintilla.

This change is triggered by CMake 3.11, which tries to build the embedded
QScintilla slightly differently. That fails because there are header
files declaring enum { SCI_CANREDO = 2016 } *and also* header files
that #define SCI_CANREDO 2016; the include order is very fragile.

Test Plan

Builds on 11.1-amd64 with both CMake 3.10 and CMake 3.11.

[adridg]

Forgot to bump PORTREVISION

[lbartoletti]

Tested and it works.
Thanks.